In Quentin, your whole posts appeared on the category and archive pages, but in Misty Look only the beginnings of your posts appear. That is the way those themes are designed. It has nothing to do with using the "more" tag.

With MisyLook, you have the opportunity to write custom excerpts for your posts. On the post editor page you should have a module called "excerpts." (If you don't see it go to screen options and be sure that the excerpt module is visible.)

Write your custom excerpt in the module. Note that it is an html editor so you can even include pictures and other formatting in your custome excerpts. If you don't know html then write your excerpt in the visual editor the switch to html, copy the code and while still in the html editor, paste the code into the excerpt module. Save or update.
Greater detail here in these 2 posts:http://wpbtips.wordpress.com/category/excerpt/